Q. Mile markers have recently been installed every tenth of a mile on Interstate 91, replacing the traditional markers every mile. What is the reason for the change? (I would rather see road funds used to repair the road surface.)

A. Mile markers have been in place along Interstate 91 for about 20 years, but the ones that are now being installed are designated as "enhanced." In other words, new and improved.

According to Adam Hurtubise, a spokesperson for the state's Executive Office of Transportation, the signs on I-91 are part of a broader effort to install more, and more readable, mile markers along the state's controlled access highways.

Existing signs are being replaced with ones that meet federal legend and retro-reflectivity standards. Just in case those terms are puzzling, here's a translation: Legend refers to the marker's content, and the style and size of the type used on it; retroreflectivity means a sign's ability to redirect light from headlights back toward the vehicle.

Hurtubise told Lifeline that unlike the old mile-marker signs, which were posted at every even mile, the enhanced ones display the route number and direction of travel as well. In addition, the project includes new intermediate mile-marker signs - not every .1 mile, but every .2 mile.

The signs are designed to improve highway safety by enabling drivers to provide better information to State Police and MassHighway personnel in the case of an accident, a disabled vehicle, road debris, traffic tie-up or other event. The goal, of course, is to reduce the response time from emergency vehicles.

But the markers, Hurtubise added, will serve another purpose as well. "By improving the accuracy of incident reporting, the new signs will also enable MassHighway to more easily track and review the crash history at specific locations ... ," he wrote in an email. "This will enable us to identify areas with frequent crashes and develop appropriate corrective actions."

It costs about $150 to make and install each new enhanced mile marker sign, and $125 for each intermediate (.2 mile) sign. Given that there are approximately 7,725 markers (on approximately 776 miles of Massachusetts highway), the total cost of materials, labor and traffic control for the project is just under $1,720,000, Hurtubise said. Federal highway funds are covering the entire cost.